Lubricant composition



United States Patent LUBRICANT COMPOSITION Peter William Brett Semmens and James Denis Summers- Smith, Norton-on-Tees, England, assignorsto Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Feb. 27, 195 6, Ser. No. 567,744 5 Claims priority, application Great Britain Mar. '11, 1955 6 Claims. (Cl. 252- 493) This invention relates to compositions of matter which 2,945,814 .Patented July 19, 1960 ice can be obtained having a Wide range of viscosity. The

orthopho'sphates themselves are in general grease-like phate is desired, the vehicle may be for example mineral oil mixed with as much as 80% by weight of, for example,

* -di(cetyl trimethyl ammonium) monohydrogen orthophosare suitable for use as lubricants of surfaces, especially metal surfaces, moving relative to one another.

Under the particular conditions which may occur at low sliding speeds and high loads and which are known as boundary conditions, the hydrodynamic film Which is established between sliding metal surfaces by orthodox lubricants is broken down, and the coefiicient of friction between the two surfaces rises considerably. This may give rise to excessive local heating and even to complete seizure of thesliding parts.

In order to overcome this deterioration of orthodox lubricants, it has been proposed to use other substances which are effective lubricants under boundary conditions,

pl'rate. In addition to mineral oil and castor oil, other suitable vehicles for use in the present invention include for example polymethyl-phenyl siloxanes, polyalkylene glycols, liquid paraflin, substantially completely halogenated hydrocarbons such as those sold under the British Registered Trademark Florube l, and esters of dicarboxylic acids. The vehicle may also be a solid such as petroleum jelly or solid polymethyl-phenyl siloxane.

Boundary lubricants prepared according to the present invention are particularly effective in the lubrication under boundary conditions of such sliding surfaces as and which are usually called boundary lubricants. For

example, long chain fatty'acids and their esters may be,

used as boundary lubricants, but these compounds are limited in having a comparatively low upper temperature at which they remain effective.

Improved boundary lubricants have been proposed in our co-pending U.S. application Serial No. 530,213, filed August 23, 1955, and now abandoned, which comprise a polyphosphate compound having as the cation a quaternary ammonium group which'is attached to at least one radical which contains at least one alkyl group having six or more carbon atoms, and a liquid vehicle in which the polyphosphate is soluble or dispersible such as a hydrocarbon or siloxane oil, or vegetable oil, or an ali- V phatic ester, or a mixture of these. In the preparation of these polyphosphate derivatives, it is usual to start with a suitable dihydrogen orthophosphate salt such as potassium dihydrogen orthophosphate and to heat it under suitable conditions to provide potassium polyphosphate, which is further treated to produce the quaternary ammonium polyphcsphate.

'We have now found that improved boundary lubricants are provided by compositions of matter which include quaternary ammonium orthophosphate salts, without the necessity of conversion to polyphosphate.

According to the present invention therefore we provide improved boundary lubricantswhich comprise an orthophosphate compound of which the cations comprise one or two quaternary ammonium groups in which the nitrogen'is attached to at leastone radical which contains at least one alkyl group having six or more carbon atoms, and a vehicle which is a lubricant and in which the orthophosphate is soluble or dispersible, such as hydrocarbon, or vegetable oil, 'or siloxane oil, or an aliphatic ester, or a polyalkylene glycol, or a grease-like solid, or a mixture of these.

Suitable quaternary ammonium groups include cetyl trimethyl ammonium, cetyl pyridinium, didecyl dimethyl ammonium, stearamidomethyl pyridinium, di-octyl dimethyl ammonium, lauryl benzyl dimethyl ammonium,

are found in bearings, particularly bearings for stainless steel shafts. The table below gives the coetficient of friction between a pair of mild steel and a pair of stainless steel surfaces sliding under boundary conditions, and it'will be seen that in most cases the efiectiveness of these boundary lubricants is not reduced by increase in temperature, and in some cases the coefiicient of friction decreases with increasing temperature. The maximum temperature at which measurements could be taken on the instrument used was 200 C., but considerable evidence exists which suggest that, subject to the thermal stability of the vehicle, these boundary lubricants are equally effective at higher temperatures than 200 C. This is in striking contrast to boundary lubricants based on fatty acids, which are subject to serious temperature limitations.

Quaternary ammonium orthophosphates suitable for use in the present invention may be prepared as follows.

200 mls. of a 10% solution of the appropriate quater nary ammonium halide, preferably the chloride or bromide, preferably at room temperature, are passed through a column of 250. gms. of a suitable exchange resin such as that sold under the British Registered Trademark Amberlite IRA 400, which has been previously activated to give the hydroxyl form by contact with aqueous sodium hydroxide solution. A 10% aqueous solution of orthophosphoric acid is added to the resulting quaternary ammonium hydroxide solution conveniently at room temperature and preferably with mixing. If the monohydrogen orthophosphate salt is required, the addition of orthophosphoric acid is stopped when the pH of the solution is 8.5. If however, the dihydrogen salt is required, the addition of orthophosphoric acid is continued until the pH of the solution is 4.5. The solution is then carefully evaporated to dryness, and the product, which is a grease-like solid, is removed.

The quantities and concentrations of quaternaryammoniu-m halide, exchange resin and phosphoric acid are not critical, but the figures given in the above example are convenient values. If the solution of quaternary ammonium halide is too dilute, there will be excessive liquid bulk to handle and evaporate, for a given weight of product. The concentration of the ort-hophosphor-ic acid should be sufliciently high to avoid excessive liquid bulk but low enough to give adequate control when the pH of the product solution is adjusted.

In most cases it is necessary to heat the mixture of orthophosphate and vehicle preferably to temperatures below 180 C., and preferably for no longer than 30 minutes. It is also preferable to stir throughout the mixmg.

I P 3 EXAMPLE 1 0.1 gram of cetyl trimethyl ammonium dihydrogen orthophosphate prepared as hereinbefore described, were mixed with 10 mls. of a mineral oil having a viscosity of 90'centistokes at 20 C. and 4.25 centistokes at 100 C., and heated with constant stirring at 230 C. for 10 min- Table 1 COEFFICIENTS F FRICTION UNDER BOUNDARY CONDITIONS [Sliding speed-0.08 cm./sec.]

Lubricant Austenitlc Stainless Steel Vehicle Ortho- 20 60 100 120 140 160 180 200 phosphate 0. O. 0. 0. O. O. C.

Table 2 Lubricant Mild Steel Vehicle Ortho- 20 60 100 120 140 160 180 200 phosphate 0. C. C. C. O. C. C. C.

Nilu .82 0.92 0.88 0.83 0. 94 0. 92 0. 87 0. 95 100% C. .09 0. 0. 12 0. l2 0. 14 0. 14 0. 14 0. 95% (1.0 .11 0.10 0. 09 0.09 0. 09 0.08 0. 08 0. 08

M.O.Mineral Oil.

Viscosity at 0., 90 centistokes. Viscosity at 100 0., 4.25 centistokes. Density 0.9 gram/0.0. at 10 C.

C 0.Castor oil.

utes. The mixture was then allowed to cool with constant stirring. Most of the orthophosphate dissolved, and thesupernatant liquor was decanted from the residue after the mixture was allowed to settle.

EXAMPLE 2 An approximately 1% solution of di(cetyl trimethyl ammonium) monohydrogen orthophosphate in mineral oil was prepared by using the same quantities and method just previously described. In this case practically all the orthophosphate dissolved, so that very little residue remain'ed on decanting.

EXAMPLE 3 0.7 gram of cetyl trimethyl ammonium dihydrogen orthophosphate prepared according to the method hereinbefore described, and 9.3 grams ofpetroleum jelly were heated together at 50 C. for 20 minutes with stirring.

All-the orthophosphate dispersed, and the mixture was allowed to cool.

EXAMPLE 4 A dispersion of 0.7 gram of di(cetyl trimethyl ammonium) monohydrogen orthophosphate, prepared according to the method hereinbefore described, in 9.3 grams of petroleum jelly was made in a similar way to the method just previously described.

EXAMPLE 5 We claim:

1. A boundary lubricant selected from the group consisting of lubricant compositions consisting essentially of between about 3 and 80% cetyl trimethyl ammonium dihydrogen orthophosphate dissolved in mineral oil, between about 3 and 80% of di(cetyl trimethyl ammonium) monohydrogen orthophosphate dissolved in mineral oil, between about 3 and 80% cetyl trimethyl ammonium dihydrogen orthophosphate dispersed in petroleum jelly, between about 3 and 80% di(cety1 trimethyl ammonium) monohydrogen orthophosphate dispersed in petroleum jelly, and between about 3 and 80% di(cetyl pyridinium) monohydrogen orthophosphate dissolved in castor oil.

2. A boundary lubricant consisting essentially of between about 3 and 80% of cetyl trimethyl ammonium dihydrogen orthophosphate dissolved in mineral oil.

3. A boundary lubricant consisting essentially of between about 3 and 80% of di(cetyl trimethyl ammonium) monohydrogen orthophosphate dissolved in mineral oil.

4. A boundary lubricant consisting essentially of between about 3 and 80% of cetyl trimethyl ammonium dihydrogen orthophosphate dispersed in petroleum jelly.

5. A boundary lubricant consisting essentially of between about 3 and 80% of di(cetyl trimethyl ammonium) monohydrogen orthophosphate dispersed in petroleum jelly.

6. A boundary lubricant consisting essentially of between about 3 and 80% of-di(cetyl pyridinium) monohydrogen orthophosphate dissolved in castor oil.

References Cited in the file of this patent UNITED STATES PATENTS 2,285,853 Downing et al. -n- June 9, 1942 2,563,506 Werntz Aug. 7, 1951 2,592,273 Goebel et al. Apr. 8, 1952 2,880,239 Semmens et a1 Mar. 31, 1959 

1. A BOUNDARY LUBRICANT SELECTED FROM THE GROUP CONSISTING OF LUBRICANT COMPOSITIONS CONSISTING ESSENTIALLY OF BETWEEN ABOUT 3 AND 80% CETYL TRIMETHYL AMMONIUM DIHYDROGEN ORTHOPHOSPHATE DISSOLVED IN MINERAL OIL, BETWEEN ABOUT 3 AND 80% OF DI(CETYL TRIMETHYL AMMONIUM) MONOHYDROGEN ORTHOPHOSPHATE DISSOLVED IN MINERAL OIL, BETWEEN ABOUT 3 AND 80% CETYL TRIMETHYL AMMONIUM DIHYDROGEN ORTHOPHOSPHATE DISPERSED IN PETROLEUM JELLY, BETWEEN ABOUT 3 AND 80% DI(CETYL TRIMETHYL AMMONIUM) MONOHYDROGEN ORTHOPHOSPHATE DISPERSED IN PETROLEUM JELLY, AND BETWEEN ABOUT 3 AND 80% DI(CETYL PYRIDINIUM) MONOHYDROGEN ORTHOPHOSPHATE DISSOLVED IN CASTOR OIL. 